How to update ios15 on 6plus

Vawul wrote:

How to update iphone 6s

to iOS 15

which is it.. 6s or 6 Plus?

You can check in Settings > General > About.. let us know the iPhone Model and Software Version

the 6 Plus cannot run iOS 15, it can only run iOS 12.

the 6s can run run iOS 15, you'd just go to Settings > General > Software Update

An iPhone 6/6plus can't be updated beyond 12.5.6, it doesn't have the hardware needed to run anything higher.

If you need a higher iOS version, you will have to purchase a newer phone.